This invention belongs to the rodenticidal art and provides a new method and compositions for reducing populations or rats or mice.
It has long been known that rats and mice must be controlled. Rats and mice are known carriers of many diseases of which bubonic plague is only the best known. The pestiferous animals also, when sharing the habitations of mankind, soil and contaminate the areas in which they live, and destroy buildings and their contents by their tunneling and nest-building. The animals also consume foodstuffs, and contaminate what they do not consume. A colony of rats in a grain-storage building can consume or destroy substantial amounts of food.
Many kinds of rodenticides have been, and still are, in use. Metallic poisons, such as arsenic and thallium compounds, are still in use, but obviously pose serious hazards to people and useful animals. Organic chemical poisons, of which warfarin is the best known, are in extremely wide use and have served well. However, rodents are developing resistance to such poisons.
Rodenticides are usually presented to rats or mice in the form of mixtures with foodstuffs. The concentration of rodenticide in the mixture is adjusted so that the rodents consume an amount of the rodenticide which is either acutely or chronically lethal. It is advisable not to make the mixture so concentrated that the rodent dies immediately, or even soon after eating. Rodents, and especially rats, are intelligent enough to understand the casual relationship between feeding and death if the time interval is very short. Thus, the best practice is to adjust the concentration of the rodenticide so that the rodents will be poisoned over a number of feedings at the poison bait.
In special circumstances, rodenticides are sometimes mixed in drinking water, or prepared as "tracking powders", which are deposited in runways used by the rodents. After the animals have walked through the loose poison powder, they lick their feet clean and thus ingest the rodenticide.
Compounds such as those used in the present invention have not previously been used for the control of rodents. The compounds are known to be fungicides and insecticides, however. Therefore, prior workers have made formulations which comprised the compounds dispersed in water and in finely powdered solids. South African Patents Nos. 73/09415 and 72/01370 supply the history of the compounds.